Checking a mic preamp without connection to audio interface
If you have a powered mic preamp connected to a mic via an XLR cable but with no further connection to an audio interface (that would typically be via a balanced 1/4" jack pickup cable), shouldn't the VU meter on the channel output level of the preamp become active when the preamp is turned on, the mic is powered with 48V phantom power, and the output level knob for the channel the mic is connected to is turned?
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If I'm understanding you correctly, yes.
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But the VU meters work on mine regardless if the pre is connected to an interface or not. |
What would that VU meter be measuring? Usually it's output (work being done).
Not sure what a VU meter would indicate when current not flowing through it. |
So what prompted this is I took delivery on Thursday of a new Sebatron Axis 200 preamp that I purchased from Soundpure as a demo unit.
I connected it to my DAW (Reaper) via my Scarlett 2i4 interface as follows: 1. XLR mic cables from two SDC's (KM184's) to Axis XLR inputs. 2. XLR mic cables from Axis XLR outputs to Scarlett XLR inputs, Scarlett mic gain controls set to 0, Scarlett phantom power off, Scarlett Line/Inst switch set to Line. 3. Scarlett USB feed to PC and DAW setup with two tracks (Channel 1 and 2 on both the Scarlett and Axis). When I power the Axis up, for each channel the Pad/Gain control knob is set to -15dB (full counterclockwise to the left), Output Level control knob is set to 0, HPF is off, phantom mic power is off. When I turn the phantom power on for each mic channel and turn the Output Level knob to the right, there is no activity on the Axis VU meters and no activity on the track level indicators in the DAW. Using same XLR cables from mics to the Axis, if I take the Axis out and go straight to the Scarlett and use it's preamps, everything works fine. I wonder if the Axis is DOA. I'll be in touch with Soundpure first thing on Monday. |
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Does the red indicator light come on when you engage phantom power? Short of any of those, I can't think why it would not be working other than the unit being damaged in some way. And since it's a demo unit, that's certainly possible. In the videos on this unit, SoundPure says they have them in use in their studio. A demo from them might have a lot of hours on it. |
Now that we know that the pre is Australian and you're (probably) American, the only other thing I can think of is that it might be set for 220V operation, when you probably want 110.
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I don’t think this would cause the problem you’re having, but you should connect the preamp output to the Scarlett 2i4 using a 1/4” plug at the 2i4. Using a xlr at the 2i4 runs it into the mic preamp which can handle only a 3.5 dbu max signal (even with switch set to line).
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So if everything works by taking the Seb out of the equation then the problem is definitely with Seb I have never used one so just guessing
First are you letting the Pre's tubes warm up ? say 5 or more minutes ? If so ::: #1 what about Bad tubes ???? is there any venting slots where you can see if the tube/s are glowing inside the pre amp (without having to take the cover off) ? It is strange it really almost sounds like maybe the phantom power is not getting to the mic circuit But if the light is on then it should be ??? Have you tried a dynamic mic and see if you get any signal in the VU meter's ??? |
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I'll try a dynamic mic but it's a moot point as I record solo guitar with SDC's and LDC's. The more I think about it, something is definetly wrong with this unit. It's going back to Soundpure. At least I have the new Motu interface coming in on Monday to start working with. |
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Thanks! |
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